Chapter 1: The Chemistry of Life Summary

Atoms and elements

  • An atom is a small unit of matter that can show element identity during a chemical reaction.
  • An element is a molecule that can be degraded by chemical reactions into simple substances.
  • Important elements in physiology include:
    • Hydrogen
    • Carbon
    • Oxygen
    • Nitrogen
  • Isotopes are atoms of elements with different neutron numbers and different atomic weights.
  • Ions are atoms that have lost or gained electrons.
  • An acid is a substance that loses an electron. It is also called an electron donor.
  • A base is a substance that ionizes when placed in a solution generating negatively charged hydroxyl ions (OH).

Chemical bonds

Chemical bonds are forces that hold atoms together to form a molecule.

The main types of bonds include the following:

Ionic bonds: This is formed from electron transfer where one atom loses one electron while one atom gains an electron. Hence, one of the ions formed carries a positive charge the other one carries a negative charge.

Covalent bond: These are bonds formed by electron sharing between two atoms involved in a reaction.

There are types of covalent bonds that include the following.

Polar bond: This is formed by attractions for electrons on atoms involved in a covalent bond resulting in an unevenly distributed charge.

Hydrogen bond: This bond is formed between polarized ends containing water molecules. The hydrogen on one water molecule with a partial positive charge attracts the oxygen on the adjacent molecule with a partial negative charge.

Organic molecules of biological importance

  • Carbohydrates: They are made up of carbon, oxygen, and hydrogen. Here are several types of carbohydrates which include the following:
    • Monosaccharides: They are building blocks for the carbohydrates molecules and serve as a source of energy in cells.
    • Disaccharides: They are formed by combining two monosaccharides.
    • Polysaccharides: They are formed by combining several monomers like glucose, a disaccharide.
  • Lipids: These are molecules containing carbon, oxygen, hydrogen and may sometimes contain phosphorus and nitrogen. They are soluble in organic solutions. They act as a source of stored energy by six-fold compared to carbohydrates.
  • Proteins: These are the largest molecules. Proteins are made up of carbon, oxygen, hydrogen, nitrogen, and sometimes phosphorus. Proteins are manufactured from 20 different amino acids. Every amino acid has an amino group.
  • Nucleic acids: These are long molecules found in the nucleus of a cell in a living organism. They are composed of nucleotides are building blocks. Each nucleotide has a 5-carbon sugar, a phosphorus group, and a base.


This refers to various chemical reactions that occur in cells relating to storage and utilization of the molecules to produce energy,

All metabolic reactions can either be catabolic or anabolic.

Cellular metabolism involves the chemical degradation of molecules in the cell.

Carbohydrate metabolism involves a sequence of cellular respiration.

These involve:
  • Glycolysis: This pathway helps in the breakdown of glucose to produce energy in the form of ATP.
  • Krebs cycle: this pathway involves a series of chemical reactions to produce energy.
  • Electron transport chain: This is a sequence of compounds of energy bonded to the inner mitochondrial membrane.

Protein metabolism has the role of synthesizing amino acids in the body. Proteins can also be directed to the electron chain to produce energy for the cell.


What three subatomic particles make up atoms? The subatomic particles that make up atoms are protons, neutrons, and electrons.

Atom – The basic unit of matter.

Nucleus – The center of the atom that is formed by protons and neutrons bound together with strong forces.

Electron -A negatively charged particle ( – ) with only 1/1840 mass of a proton that surrounds the nucleus.

How are all of the isotopes of an element similar? – Because they have the same number of electrons, all isotopes of an element have the same chemical properties.

Element – A pure substance that consists entirely of one type of atom.

Isotope – Atoms of the same element that differ in the number of neutrons they contain.

In what ways do compounds differ from their component elements? – The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed.

Compound – A substance formed by the chemical combination of two or more elements in definite proportions.

What are the main types of chemical bonds? – The main types of chemical bonds are ionic bonds and covalent bonds.

Ionic Bond – Formed when one or more electrons are transferred from one atom to another.

Ions – Positively and negatively charged atoms because of transferred electrons.

Covalent Bond – Formed when moving electrons actually travel about the nuclei of both atoms and share them between atoms.

Molecule – The smallest unit of most compounds.

van der Waals forces – When molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules. It’s named after the scientist who discovered them.

How does the structure of water contribute to its unique properties? – Because water is a polar molecule, it is able to form multiple hydrogen bonds, which account for many of water’s special properties.

Hydrogen Bond – The attraction between a hydrogen atom on one water molecule and the oxygen atom.

Cohesion – An attraction between molecules of the same substance.

Adhesion – An attraction between molecules of different substances.

How does water’s polarity influence its properties as a solvent? – Water’s polarity gives it the ability to dissolve both ionic compounds and other polar molecules.

Mixture – A material composed of two or more elements or compounds that are physically mixed together but not chemically combined.

Solution – Formed when ions gradually become dispersed in water.

Solute – The substance of a solution that is dissolved.

Solvent – The substance of a solution in which the solute dissolves.

Suspensions – Mixtures of water and non-dissolved material.

Why is it important for cells to buffer solutions against rapid changes in pH? – Buffers dissolved in life’s fluids play an important role in maintaining homeostasis in organisms.

pH Scale – A measurement system used to indicate the concentration of H+ ions in solution.

Acid – Any compound that forms H+ ions in solution.

Base – A compound that produces hydroxide (OH-) ions in solution.

Buffers – Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.

What elements does carbon bond with to make up life’s molecules? – Carbon can bond with many elements, including hydrogen, oxygen, phosphorus, sulfur, and nitrogen to form the molecules of life.

What are the functions of each of the four groups of macro-molecules?
Living things use carbohydrates as their main source of energy. Plants, some animals, and other organisms also use carbohydrates for structural purposes. Lipids can be used to store energy. Some lipids are important parts of biological membranes and waterproof coverings. Nucleic acids store and transmit hereditary, or genetic, information. Some proteins control the rate of reactions and regulate cell processes. Other form important cellular structures, while still others transport substances into or out of cells or help to fight disease.

Smaller units that form polymers.

Form macro-molecules by a process known as polymerization.

Compounds made up of carbon, hydrogen, and oxygen atoms, usually in a ratio of 1 : 2 : 1. Living things use carbohydrates as their main source of energy. Plants, some animals, and other organisms also use carbohydrates for structural purposes.

Single sugar molecules.

Made mostly from carbon and hydrogen atoms. The common categories of lipids are fats, oils, and waxes. Lipids can be used to store energy. Some lipids are important parts of biological membranes and waterproof coverings.

Nucleic Acids
Macro-molecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus. Nucleic acids store and transmit hereditary, or genetic, information.

Individual monomers of 5 carbon-carbon sugar, a phosphate group (-PO4), and a nitrogenous base that make up nucleic acids.

Macro-molecules that contain nitrogen as well as carbon, hydrogen, and oxygen. Some proteins control the rate of reactions and regulate cell processes. Other form important cellular structures, while still others transport substances into or out of cells or help to fight disease.

Amino Acids
Compounds with an amino group (-NH2) on one end and a carboxyl group (-COOH) on the end that make up proteins.

What happens to chemical bonds during chemical reactions?
Chemical reactions involve changes in the chemical bonds that join atoms in compounds

Chemical Reaction
A process that changes, or transforms, one set of chemicals into another. Mass and energy are conserved during chemical transformations.

The elements or compounds that enter into a chemical reaction.

The elements or compounds produced by a chemical reaction.

How do energy changes affect whether a chemical reaction?
Chemical reactions that release energy often occur on their own, or spontaneously. Chemical reactions that absorb energy will not occur without a source of energy.

Activation Energy
Energy needed to get a reaction started.

What role do enzymes play in living things and what affects their function?
Enzymes speed up chemical reactions that take place in cells. Temperature, pH, and regulatory molecules can affect the activity of enzymes.

A substance that speeds up the rate of a chemical reaction.

Proteins that act as biological catalysts.

The reactants of enzyme-catalyzed reactions.

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